This invention relates to a prosthetic device. In particular it relates to a torque absorber and sensing element that permits limited movement of a joint between two prosthetic members while providing a signal upon an excessive compressive force between the two elements.
Following the amputation of a lower limb, it is important that the amputee be fitted with a prosthesis as early as possible in order to effect a rapid recovery and to provide early familiarity with the use of the prosthetic device. Due to the nature of amputation, the residual limb is particularly sensitive to the pressure of a prosthesis when initially fitted. In order to attain a balance between the sensitivity and the requirement for early fitting, the prosthetist will ordinarily fit the amputee with a temporary prosthetic device within a period of a few days following the amputation. It is not the intent of the prosthetist to have the patient become completely mobile on this temporary prosthesis; rather, it is the intent of the prosthetist to carry the patient through the healing stage of the residual limb in a partially ambulatory state. In the past, it has been the practice of the prosthetist to tell the patient not to exceed, for example, forty pounds of force on the residual limb when using the temporary prosthetic device. It is unrealistic to expect a new amputee to be able to sense a particular force in a residual limb, particularly when the residual limb is sensitive to undue pressure. As a result, a good deal of guesswork coupled with discomfort on the part of the patient has occurred in the fitting of prosthetic devices.
In addition to the problem of attempting to establish a maximum pressure on the residual limb, a new amputee needs a prosthetic device that is similar to the natural limb which has been removed. In particular, it is appropriate to provide a limited degree of flexibility at or in the vicinity of the missing joints, such as the knee and the ankle. During the temporary phase, that is, during the familiarization period with the temporary prosthetic device, it is appropriate to eliminate a fully operative knee joint as use of such a prosthetic knee requires a particular acquired skill. During the familiarization period, it is appropriate to reduce to a minimum the learning requirements, hence, eliminating the knee joint is appropriate. Nevertheless, the patient needs some motion between the residual stump and the bearing surface or floor. If there is no capability to rotate between the stump and the floor, the prosthesis will rub or chafe the residual limb to the point where blisters or ulcers are formed. Accordingly, there must be some flexibility. This is particularly important where the patient is in the preliminary or learning phases of adjustment to a prosthetic device. Such flexilibity is described in U.S. Pat. No. 4,134,159, issued on Jan. 16, 1979 to the inventor herein. However, this torque absorber is normally located at the upper end of the prosthetic device, in particular between the socket and the upper pylon. Since this type of torque absorber is generally molded into the cosmesis, it is not appropriate for a temporary prosthetic device. Furthermore, this particular type of torque absorber is not appropriately combined with a pressure sensing system because of the nature of its structure.
Accordingly, it is an object of the present invention to provide a prosthesis of at least two elements that permits limited movement between the two elements.
It is a further object of this invention to provide a prosthesis that includes a pressure sensing system.
It is still another object of this invention to provide a prosthesis wherein a pressure sensing system is responsive to a predetermined pressure.
It is still further an object of this invention to provide a prosthesis which combines the motion of a torque absorber along with the pressure sensing capability.
It is also an object of this invention to provide adjustability to the pressure sensing system.
The present invention is directed to overcome one or more of the problems as set forth above and to meet at least the objects as set forth.